I'm testing Zen (https://zen-browser.app/) on macOS since a while back. Updates seem to lag behind the upstream by everything from 2 to 10 days. Every now and then a Zen-specific update shows up. So far the experience has been good. I don't know how true to their word of protecting privacy the authors really are, as my web proxy shows that the browser connects with Google infrastructure at sporadic intervals through the day even when the browser is sitting idle with no loaded tabs or active extensions. My feeling is that it is too frequent to be the auto-update check. I really hope I'm wrong or goofed up with keeping an eye on its network chatter.